Organic EL panels provided with an organic electroluminescent element (hereinafter, also referred to as an “organic EL element”) utilizing the electroluminescence of an organic material currently receive attention. The organic EL element emits light by recombining holes injected from an anode and electrons injected from a cathode in a light-emitting layer provided between the electrodes. When used as display panels for thin profile display devices, the organic EL panels are superior to liquid crystal display devices in characteristics such as high contrast and low power consumption. The organic EL panels are also expected to be used in applications other than display devices, such as lighting.
The organic EL element includes, in the order from the substrate side, a lower electrode, an organic light-emitting layer, and an upper electrode. A structure in which the lower electrode is a transparent conductive film, the upper electrode is a metal layer, and the light is emitted from the lower electrode side is called a bottom emission (BE) structure. In contrast, a structure in which the lower electrode is a metal layer, the upper electrode is a transparent conductive film or a semi-transparent metal film, and the light is emitted from the upper electrode side is called a top emission (TE) structure. Another structure is proposed in which the lower electrode and the upper electrode are transparent or semi-transparent and the light is emitted from both sides.
Patent Literatures 1 to 9 disclose various stack structures of the top-emission-structured organic EL element, for example.